The accuracy and clogging of microchannels are important for assessing the quality of lab on chip (L-O-C) devices. The clogging affects the fluid mixing efficiency and influences the bonding of substrate. In this paper, inexpensive and quick method for microchannel fabrication in polymethyl methacrylate (PMMA) while reducing the thermal damage is introduced. Accordingly, the substrate was covered with a thin layer of water during CO2laser ablation. The effect of water cooling on the clogging formation, heat affected zone and the microchannel geometry in terms of depth and width is investigated. Clogging formation mechanism in the intersection of Y-channel is studied to improve its quality for microfluidics applications. During the experimental work, the CO2laser power was varied from 2.4 to 6 W at scanning speed from 5 to 12.5 mm/s. The results showed that covering the PMMA substrate with a thin layer of water prevented clogging formation and reduced the heat affected zone.
Over the last few decades, miniaturization has become the key aspect of driving evolution of modern technology. The CO 2 laser is an inexpensive, flexible, and fast device for fabricating microfluidic chips. Thermal damages associated with such a process are considered the big challenge for microfluidic device developers. This article evaluates the quality of polymethyl methacrylate microchannels fabricated by the CO 2 laser. Experiments were conducted in the air (dry) and underwater by leaving a thin water layer on the top surface of the polymethyl methacrylate substrate. The effect of laser power and scanning speed on performance characteristics, such as the microchannel aspect ratio, surface roughness, and heat-affected zone was studied. Taguchi's experimental design with grey relational analysis was used for multiobjective optimization of the laser micromachining parameters. Analysis of variance was also employed to determine the most significant control factors that affect the microchannel quality. The results indicated that the cooling effect of the underwater method has a significant effect on decreasing the extent of thermal damage while increasing the aspect ratio. Laser power is the most significant factor on the performance characteristics followed by scanning speed and pulse rate. Grey relational analysis is efficient in selecting the optimum conditions regarding the performance characteristics.
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